U.S. Pat. No. 4,804,615 discloses a method for forming metallic conductor patterns with solderable connection regions, in which the starting point is an electrically insulating, flat substrate laminated with copper on both sides. After through-contact holes have been drilled, a copper layer, which also extends over the walls of the hole, is deposited from a chemical deposition bath. An electrolytic resist is then applied to this copper layer and covers everything except the subsequent connection regions, so that copper and a tin/lead alloy can be deposited here electrolytically one after another. The tin/lead alloy forms a final surface of the connection regions which can be soldered. After the complete removal of the electrolytic resist, an etch resist is applied and, with the exception of the connection regions, covers all the regions of the subsequent conductor pattern. After this, all those regions of the chemically deposited copper layer which do not correspond to the conductor pattern, and of the copper lamination, are etched away down to the surface of the substrate. During this etching process, it is not only the actual etch resist but also the etch-resistant final surface of the connection regions which protect the copper located beneath them from the etching attack. After the complete removal of the etch resist, a solder-stop lacquer is then applied, which covers everything except those connection regions of the conductor pattern which can be soldered.
U.S. Pat. No. 4,608,274 discloses a further method for forming metallic conductor patterns with connection regions which can be soldered, and the starting point for the method is a pre-drilled, electrically insulating, flat substrate. After the non-electrolytic deposition of copper to both sides of the substrate and in the holes, an etch resist is applied to the copper layer, and, with the exception of the subsequent connection regions, covers all the regions of the subsequent conductor pattern. An electrolytic resist is then applied, and covers everything except the subsequent connection regions, so that copper and a tin/lead alloy can be deposited electrolytically here one after another. Following the complete removal of the electrolytic resist, all the regions of the exposed copper layer are etched away, down to the surface of the substrate; and in the region of the conductor pattern, the etch resist and the etch-resistant final surface of the connection regions protect the copper layer located beneath them from the etching attack. Following the complete removal of the etch resist, a solder-stop lacquer is also applied again, and covers everything except the connection regions of the conductor pattern which can be soldered.
WO 95/29573 discloses a further method for forming metallic conductor patterns having connection regions that can be soldered and/or bonded on electrically insulating substrates. This method comprises the following method steps:
a.) Applying a metalization to the substrate; PA1 b.) Applying an organic, electrolysis-resistant and etch-resistant protective layer to the metalization in an electrolytic dip-coating bath; PA1 c.) Removing the protective layer in the subsequent connection regions by means of laser radiation; PA1 d.) Electrolytically depositing an etch-resistant final surface which can be soldered and/or bonded onto those regions of the metalization exposed in method step c); PA1 e.) Removing the protective layer, at least in the regions directly adjacent to the subsequent conductor pattern, by means of laser radiation; PA1 f.) Etching those regions of the metalization exposed in method step e) down to the surface of the substrate. PA1 an injection-molded, three-dimensional substrate made of an electrically insulating polymer, PA1 polymer studs arranged over the area of the underside of the substrate and formed at the same time during the injection molding, PA1 external connections formed on the polymer studs by a final surface that can be soldered, PA1 conductor trains, formed at least on the underside of the substrate, which connect the external connections to internal connections and PA1 at least one chip arranged on the substrate, whose connections are electrically conductively connected to the internal connection.
The advantages of the method outlined above reside in particular in the fact that only a single organic protective layer has to be applied in an electrolytic dip-coating bath and, following a first structuring by means of laser radiation, serves as an electrolytic resist and, after a second structuring by means of laser radiation, serves as an etch resist, and also does not have to be removed following the formation of the conductor pattern. The protective layer previously already used as a electrolytic resist and etch resist can, if appropriate, additionally be used further as a solder-stop mask.
In WO 96/09646, a so-called Polymer Stud Grid Array (PSGA) is described which combines the advantages of a Ball Grid Array (BGA) with the advantages of MID technology. The description of the new design type as a polymer stud Grid Array (PSGA) was carried out in this case following the model of the Ball Grid Array (BGA), and the term "Polymer Stud" is intended to refer to the polymer studs formed at the same time during the injection molding of the substrate. The new design type, suitable for single-chip, few-chip or multi-chip modules, comprises
U.S. Pat. No. 4,289,575 discloses a method of producing printed circuits in which, firstly, a conductor pattern is produced by means of conventional photo-etching technology, and its individual conductors remain connected to one another via connecting webs. An electrically insulating, electrolysis-resistant and etch-resistant first film is subsequently applied in such a way that only the connection regions of the conductor pattern and the connecting webs remain free. After that, an electrolysis-resistant second film is applied to the connecting webs, whereupon a final surface which can be soldered and/or bonded is applied, by means of electrolytic metal deposition, to the exposed connection regions of the conductor pattern. Following the removal of the second film, the connecting webs can then be etched away selectively.